Influence of Caliper Piston Wall Thickness and Hard Anodizing on Thermal Transfer and Seal Rollback Stability in Hydraulic Disc Brakes

Thermal stability and sealing reliability are critical performance parameters in hydraulic disc brake systems, especially under high-energy braking conditions where elevated temperatures directly influence brake fluid behavior and elastomer seal durability. Lightweight design trends increasingly encourage reduction in caliper piston wall thickness to optimize mass and response characteristics; however, such modifications alter the thermal conduction path and transient heat distribution within the piston–seal interface. This study investigates the combined effect of 50% reduction in aluminum caliper piston wall thickness and increase in hard anodizing thickness from 20 µm to 50 µm on heat transfer characteristics and piston seal rollback consistency. A comparative analytical and experimental approach is adopted to evaluate thermal resistance changes due to variation in anodic oxide layer thickness and piston geometry. One-dimensional thermal modeling is correlated with controlled laboratory testing, including thermal cycling and hydraulic pressure cycling, to assess piston surface temperature, brake fluid exposure temperature, and elastomer seal recovery behavior. Special emphasis is placed on 70 Shore A elastomer piston seals designed for a functional rollback range of approximately 50 µm, where viscoelastic stability and compression set behavior become dominant factors. Results indicate that increased anodizing thickness enhances the thermal barrier effect by reducing conductive heat transfer toward the brake fluid, while reduced piston wall thickness lowers thermal mass and increases transient piston surface temperature. These competing effects significantly influence seal aging, modulus variation, and rollback repeatability over thermal cycles. The study further evaluates cost-effective elastomer formulation strategies and material selection considerations to improve high-temperature durability without compromising manufacturability. The findings provide practical design guidelines for optimizing the interaction between piston geometry, surface coating thickness, and elastomer seal characteristics to achieve consistent rollback and improved thermal robustness in modern hydraulic brake systems